Tuesday, April 7, 2009

The sun and global warming.

A large ice shelf in Antarctica has finally separated from the continent. This is a shelf that has been unchanged for a better part of the century, but over the past two decades has receded enough to break off. Climatologists are pointing to this as hard evidence of the severe global warming currently occuring on Earth.

I initially read about this story on Fark.com, a news feed website with a healthy comment section for each story posted. The comments, as they tend to do on this site, were extremely diverse but had a stronger-than-usual dose of global warming deniers. An argument brought up repeatedly by this crowd was that the Sun is chiefly responsible for the increase in global temperatures, so we shouldn't worry about anything.

I don't buy it at all.

I will preface this entire argument with the following: I am NOT a climatologist, and my expertise lies in magnetospheric physics.

That said, I have a huge problem with the "Sun does teh warmnigs!" argument. I've already discussed that we are in a historically weak AND long solar cycle, and that we are floating in the duldrums of a pathetically long solar minimum (see this post and this post). While I focus on sunspot number when discussing the solar cycle, solar energy output follows the same pattern. This means the amount of energy delivered to the Earth by the Sun is less during solar minimum than solar maximum. We actually have a fairly good proxy to demonstrate that weak solar activity corresponds to global cooling in the Maunder Minimum.

The current solar cycle and the loss of this section of the Antarctic ice shelf is completely contradictory to their claims that the degree of global warming we are currently experiencing is a natural, solar driven process. If we were in a period of strong solar activity (or were within 5 years of solar max), the deniers might have a point -- but the exact opposite is currently true. Given this evidence alone, I reject the hypothesis that our global warming situation is due entirely to changes in solar activity (or even strongly influenced by it!)

Some caveats that must be posted: 1) The relationship between solar activity changes and our climate is complicated and far from understood. 2) I am not a climatologist. Nor am I a true solar physiscist. I'll see if I can scrounge up a specialist to comment on this. 3) This argument completely neglects the evidence demonstrating human influence on global warming.

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